I'm currently running a mythic game that has every character being immortal. Arranging the game in this way encourages the PCs to take advantage of downtime, both in the making of items and the helping of their descendents in various subtle and decidedly non-subtle ways. Since levels are story awards, and not enough time has elapsed since the beginning of the world for there to be huge piles of treasure sitting around, there is no incentive for the group to split and go adventuring on their own.
Because I wanted the nonmagical smiths of the setting to make really cool items, I made it so that smiths could essentially make magic weapons nonmagically, and without XP, with the tradeoff being that it takes years.
I made it so that the Craft DC of the magical component was 30, and it was priced in copper pieces rather than silver pieces. A smith who is able to complete it by taking 10 the entire time takes 4 years to make a +1 weapon, and with the assistance rules I added on to this process, it takes 10.5 years for a +2 weapon and the two people crafting having take 10 results of 40 and 30.
Other powers can be added besides straight combat bonuses, and all require special components to do. This requires the ability to give a firm "NO!" to the players on occasion., both on the appropriateness of the powers and what will be required for the special components. My group is pretty flexible and has a good idea of the mood I'm trying to evoke.
Almost forgot. In exchange for the massive amount of time spent, the plusses on the weapon are not subject to dispelling, disjoining, and aren't suppressed in an antimagic field. It's craftsmanship, not magic. Haven't yet decided on the special abilities, as it hasn't come up, but I know I'll have to make a ruling eventually.
An example of this in action:
The kingdom controlled by the mortal descendents of Wesn the Mighty was overrun by goblins (essentially humanoid locusts IMC). He's already faked his death and is trying to say out of the limelight because he's made the Grand-daddy of all Dracoliches rather angry with him. He notes that the last daughter of the family is pregnant, and starts working on a smithing masterpiece, hoping that the eventual child will be inclined to take up the sword.
Calculations indicate that, even with the help of another weaponsmaster in the group, it will take about 11 years to finish a +2 bastard sword. They had already come into the materials necessary, so work begins right away. The scout and the spellcaster each go to work, the scout attempting to find the goblin nest/hive and the other piecing together spells of protection (all spells are unique now, since magic is new). Meanwhile, the "face" of the group begins spreading a prophecy about the one who will save the land from the goblins (Wesn's great-to-the-nth-granddaughter, of course; the player's own idea), with the intention of eventually making the girl able to gather an army around her. All during downtime, narrated out with maybe a few die rolls to keep things out of dispute and quick.
11 years later, the scout's found out where they need to go, the spellcaster has his spells together, and the weaponsmiths have finished the bastard sword. The little girl, who has actually taken quite readily to running things through with pointy objects, now gets to practice with the real weapon, and downtime ends.
This kind of thing won't work for all campaigns, and so far I've limited it to just weapons and armor. But that's how it works for me so far, and it works well for the players and the game.